1. Field of the Invention
This invention relates to a feed device for a magnetic head, and more particularly to a feed device for a magnetic head for performing the recording into a cassette type magnetic disc or reproducing therefrom.
2. Description of the Prior Art
Recently, there has been developed an electronic still camera system wherein an image pickup device such as a charge coupled device (CCD) or an image pickup tube is combined with a recording device using a magnetic disc inexpensive as a recording medium and yet having a comparatively high memory capacity, a subject is still-photographed pure-electronically and recorded into a rotating magnetic disc, and the reproducing of an image is carried out by a television system, a printer or the like, and has become the object of public attention.
In an image recording or reproducing system using such a magnetic disc as described above, a magnetic disc having a diameter of about 50 mm is used, and further, the feed pitch of the magnetic head is about 100 .mu.m, which is by far smaller than that of an ordinary floppy disc, and consequently, the magnetic head sould be moved with very high accuracy. Normally, in the feed device for the magnetic head of the conventional floppy disc, a head carriage carrying the magnetic head is moved by a stepping motor directly through a rotation-linear movement converting mechanism.
However, if the system, in which the head carriage is moved by the stepping motor directly through the rotation-linear movement converting mechanism, is applied to the above-described feed device for the magnetic head requiring the aforesaid small feed pitch, then the number of steps of the stepping motor should inevitably become small. Thus, the errors in rotation of the stepping motor are not eliminated, whereby the accuracy in pitch feed of the magnetic head is disadvantageously deteriorated. On the other hand, if it is to be tried to use a reduction gear mechanism consisting of a plurality of spur gears to materialize the feed of the magnetic head with high accuracy, then a multitude of gears is required to obtain a high reduction ratio, and moreover, a large installation space for the multitude of gears is required. In consequence, as the feed device for the magnetic head used in an electronic camera or reproducer using the magnetic disc of a small diameter and limited in space, it is not proper to use the ordinary gear reduction mechanism consisting of the spur gears. Further, in the cassette portion of the cassette type magnetic disc used for the electronic still camera system, there are provided a misrecord preventive pawl for preventing a recorded track from being recorded again, a counter mechanism for indicating the number of recorded tracks and the like. In consequence, in the electronic camera or the reproducer, it is necessary to provide a detecting mechanism for the misrecord preventive portion, a counter driving mechanism and the like at associated positions, respectively. In consequence, it is extremely difficult to provide the gear mechanism to obtain a high reduction ratio so that the above-described mechanisms can be provided.